Coupled or de-coupled cabinents

Hi All-

I just removed the 6.5" woofer from my B&W Matrix 805's (walnut) and purchased some Scan Speak D2905/990000 tweeters and four (4) filters from Meniscus. I sent him the 805's to measure the 6.5".

He gave me the recommended front baffle dimensions and distances for the driver placement.

However this 2-way will be the top of a bi-amplified 3-way system.

The 2-way will sit atop a pair of 10" woofers Wilson Watt or Joseph Pearl style.

The question I have is should I make the enclosure separate or as a single cabinet?
 

wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
Sounds just like what I want to do (when I finally get the time). I was originally going to make it coupled, either with some tricky baffling, or two boxes bolted together, but changed my mind and decided decoupled was better (after some input from another person).

Decoupled gives you a lot more flexibility placement wise, and should (I think) be a lot easier to implement.

One concern I had was vibrations from the sub cabinets, but I guess if they are built well enough that shouldn't be an issue :)

edit: I'm interested to see what others think :)

Tony.
 
Hi Tony-

I would agree vibration from the woofer cabinet is a concern but as most people attempt, it should be a structurally sound box.

I will have 1.25" thick panels with heavy cross bracing for the woofer section and 1" for the top.

The enclosure will be rigidly attached but should they be one or seperatable is the question.

Currently I have the 2 805's on stands, 2 woofers on stands and all associated gear on stands.

Time to consolidate and go 2 full range enclosures free standing.


Thanks again for your input.. Currently I am leaning towards two enclosures with a pad between them then bolted together.
 
With woofers we are talking wavelength of more than 1 m. So a front baffle vibrating 1/10 mm will not hurt much. Wavelenght @20 kHz is 17 mm - and some 1/10 mm would be already 1% of it. So decoupling woofer and tweeter cabinets seems to be a good idea.

What I would pay special attention to: If the woofer is mounted vertically, it will induce a torque in its cabinet, that might result in a small angular movement to and fro. Putting the tweeter enclosure on top of the woofer cabinet would ampfy that movement. So it seems more important to keep the cabinet firmly to the ground than to minimize its inner vibration.
 
rabstg said:
... All of the answers are there.

Probably... if you know what to look for.
I found this link, which seems to be representing the manufacturer, and include data sheets:

http://www.d-s-t.com/scs/dataover/tw.htm

However, to a novice like me, it seems to be small variations over the (more or less) same thing. (or have I mis-understood something entirely?)

Jennice
 
Hi Jennice-

That is just vendor propaganda...

GOOGLE search and read reviews, comments and real life experiences of others.

When you’re tired of reading and seeing the same information in multiple places THAT is when you are becoming educated on a subject or topic.

It doesn't make you an expert like some people believe but at that point you are then able to make informed decisions.
 

wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
I was actually considering using spikes with (with the pads used for hard floors)...... and just sitting them on top of the woofer cabinets, which would be a bit like speaker stands :)

if you keep them completely decoupled, you can angle the two ways differently to the woofer cabinets, which may be advantageous under certain circumstances???

Tony.
 
I don't know of any situation where turning the woofer a few degrees one direction or another to accommodate the mid/tweet imaging would detrimental to the low frequencies.

I think their wavelength would be long enough to negate the slight change.

I hope to build an "example" enclosure for my cabinetmaker in the next couple of weeks. Then I will have some good unfinished test boxes made. If the test boxes work well, I will have him make some furniture grade heavy-duty cabinets.

I hope to get pictures of each phase.
 
Coupled or uncoupled, I dont think the SQ will be effected either way. The vibrations caused by the woofer in the enclosure is of the same frequency that the woofer will be playing. If you are truely concerned about the woofers making the 2 way enclosure vibrate to hell, then use the dual opposing woofers method. put 2 woofers in the lower cabinets each and put them on oppostie sides. The inertial forces of the cones moving and air pressure created will cancel each other out for no net force. I had a subwoofer enclosure built using this method. It had two balanced tempests and 4 balanced ports. 2 ports and a woofer on each side of the enclosure. When operated at full volume I couldnt manage to get even a dime on its edge to fall. With that in mind, coupling the 2 ways is only a matter of whether or not you wish to do it. If you have any reason you'd like to seperate the 2 ways from the subs then go for a uncoupled design. Keep in mind that the amount of energy you are coupling is minimal and should have little if any effect at all on the system. It will surely not be an audible effect. Think instead about the differences between connected and unconnected speakers as far as moving the speakers, cosmetics, etc...
 

wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
The example I was given was more to do with sub placement than anything. If they are decoupled you can (if necessary) move the sub cabinets somewhere completely different to the smaller two ways. thus getting optimal bass response without affecting your imaging :)

Tony.